In different transmission systems, e.g. in analog or digital telecommunication systems, the system transmitting voice, sound, data etc. signal has to be adapted according to different requirements set by different markets. In this context the term `market` is intended to generally mean one country, market area, standard or similar having signalling system parameters, such as impedance, voltage, signal type and similar, of its own. In other words, two markets, such as e.g. Germany and USA, do have different signalling parameters, ie. signal types, communication protocols, impedances, voltages etc. A transmission system, in turn, can include all kinds of tele-equipment, such as various exchanges and switching devices, e.g. transistors, relays and similar devices.
There is a need for making an easy and reliable selection between various signalling systems to meet the requirements of the several markets. However, the known arrangements, eg. circuit boards, have not been able to perform a software aided selection between the different markets since they are provided with only e.g. one single switch due to, for instance, essential large space requirements, power consumption, reliability and costs of one such switch. Different signalling stages (voltage levels) for the switch (0V, +5V, -48V, etc.) have been selected by manually changing the strappings on a board, and thus the software based selection has caused difficulties.
The known telephone exchange means (such as Telefonaktiebolaget LM Ericsson's MD110) are, in turn, provided with a standard backplane interface and board positions suitable for various kinds of circuit boards or cards, such as digital or analog trunk line boards, extension boards and similar.
Each such board position has a certain maximum power or watt consumption. The boards of known type consume an essentially great amount of power due to, among other things, auxiliary devices, such as relays, transistors and similar and therefore the functions of one board are generally divided into several boards to avoid an exceeding of said power limitation. The prior art manner to form the required signalling system, according to which alternative components were positioned on the same board, requires an additional space due to space requirements of the components on the board, and therefore more boards were needed. The boards are of standard size, and therefore the number of relatively big components positioned on one single board is limited. In addition, the number of channels has been low in known arrangements. This all together has led into a high number of circuit boards or cards in one switchboard or telephone exchange, which in turn has lead to a high space requirement and power consumption.